Power storage device

Abstract

Provided are an electrode for a power storage device having much better charge/discharge characteristics and a power storage device using the electrode. A plurality of cavities is provided in a surface of an active material layer over a current collector. A graphene covering the active material layer facilitates rapid charge/discharge and prevents breakdown of the current collector caused by charge/discharge. With improved charge/discharge characteristics, an electrode for a power storage device which does not easily deteriorate and a power storage device using the electrode can be provided.

What is claimed is: 
     
       1. A power storage device comprising a negative electrode comprising:
 a current collector; 
 an active material layer over and in contact with an entire top surface of the current collector; and 
 a protective layer over and in contact with a vertex of the active material layer, 
 wherein an etching rate of the protective layer is lower than that of the active material layer, 
 wherein a plurality of cavities is formed in the active material layer and the protective layer, and 
 wherein the active material layer has a width greater than or equal to 0.1 μm and less than or equal to 1 μm. 
 
     
     
       2. The power storage device according to  claim 1 ,
 wherein the plurality of cavities is arranged at regular intervals. 
 
     
     
       3. The power storage device according to  claim 1 ,
 wherein the plurality of cavities is arranged in a matrix. 
 
     
     
       4. The power storage device according to  claim 1 , wherein the active material layer has a honeycomb structure. 
     
     
       5. The power storage device according to  claim 1 , wherein the active material layer has a truss structure. 
     
     
       6. A power storage device comprising a negative electrode comprising:
 a current collector; 
 an active material layer over and in contact with an entire top surface of the current collector; and 
 a protective layer over and in contact with a vertex of the active material layer, 
 wherein an etching rate of the protective layer is lower than that of the active material layer, 
 wherein a plurality of cavities is formed in the active material layer and the protective layer, and 
 wherein the active material layer has a width greater than or equal to 0.1 μm and less than or equal to 1 μm, and has a height greater than or equal to 0.5 μm and less than or equal to 100 μm. 
 
     
     
       7. The power storage device according to  claim 6 , wherein the plurality of cavities is arranged at regular intervals. 
     
     
       8. The power storage device according to  claim 6 , wherein the plurality of cavities is arranged in a matrix. 
     
     
       9. The power storage device according to  claim 6 , wherein each of the plurality of cavities has a hexagonal structure. 
     
     
       10. The power storage device according to  claim 6 , wherein each of the plurality of cavities has a triangular structure.